Method of manufacturing a pipe liner for installation in an existing conduit

ABSTRACT

A thermoplastic liner for installation in an existing conduit is manufactured in folded form and spooled for storage. The liner is then reheated to make it pliable for installation and pulled into the conduit. Steam under pressure is used to round the installed pipe. The leading end of the liner may be restricted by an end clamp which enables hot fluid to pass completely through the pipe and heat the full length, or by an inflatable plug which is displaced to the leading end of the liner after installation. Methods and apparatus for the manufacturing of the liner include extruding heated thermoplastic pipe material through a die to form a tubular shape, shaping the extruded tubular plastic material to the folded form and cooling to provide a liner with a memory for the folded form.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/034,918,filed Mar. 19, 1993, which is a continuation of application Ser. No.07/612,163, filed Nov. 9, 1990, now abandoned, which is a divisional ofapplication Ser. No. 07/180,904, filed Apr. 13, 1988, now abandoned,which is a continuation-in-part of application Ser. No. 07/076,973,filed Jul. 28, 1987, now U.S. Pat. No. 4,867,921, which is acontinuation-in-part of application Ser. No. 06/846,322, filed Mar. 31,1986, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to improvements in methods and apparatusfor installing a replacement pipeline section inside an existingunderground conduit such as a pipeline section in need of repair orreplacement. The present invention is particularly concerned with theinstallation of a replacement pipeline section within building sewersintersecting sewer mains, within other lateral pipelines, intersectingmain pipelines, within pipeline sections that may include curves andabrupt bends, and within still other pipeline sections which areintersected by building sewers, the connections of laterals which wouldbe difficult to locate after a new pipeline section is installed withinthe existing pipeline section.

Various processes and apparatuses have Open suggested for repairingunderground pipelines such as sewer lines and the like, with theexisting pipeline remaining in place underground, by installing withinthe existing pipe a flexible membrane or liner of plastic or byinserting into the existing pipe a new plastic pipe.

In one known process, pipes are lined with a flexible plastic Such aspolyethylene. According to this process the liner is installed throughinsertion pits at intervals along the pipeline, making the processexpensive.

According to another process, shown in, for example, U.S. Pat. Nos.3,927,164 and 4,064,211 a flexible tube is turned inside out as it isinflated and blown into a pipeline section from one end of the section.This process is expensive because it requires special equipment,extensive heating and expensive materials.

The above mentioned processes and most others use a flexible orsemi-flexible liner which is not capable of withstanding any appreciableexternal hydrostatic or earth pressures. Thus the existing pipe may notbe properly repaired since if any part of it is broken away, the linercan possibly collapse from external pressure of any magnitude, such aspressures, for example, which exceed about 4 pounds per square inch.

Both Thomas et al U.S. Pat. No. 4,394,202 and Harper et al U.S. Pat. No.2,794,758 also disclose processes of inserting flexible tubing into anexisting pipeline as a lining membrane for that pipeline. Thomasdiscloses a method of attaching the flexible tubing to the existingpipeline using an expandable short section of adhesive-coated rigidplastic. Both the Thomas and Harper processes have the same drawbacks aspreviously mentioned with respect to other prior processes usingflexible membrane material in that they lack the necessary hoop strengthto withstand external earth and hydraulic pressures.

Others have suggested inserting a rigid tube inside the existingpipeline in need of repair. For example, in the published Britishapplication No. 2,084,686 an oversized round rigid plastic tube isflattened or otherwise reduced at the job site and then inserted coldand rigid into the existing pipeline through a large excavation at amanhole. After insertion, the plastic tube is expanded using heat andinternal pressure. The plastic tube is expanded against the existingpipe.

According to British Patent No. 1,580,438, an existing underground pipeis lined with a plastic liner tube made of a plastic material such aspolyethylene or polypropylene having a plastic memory. The liner tube ismanufactured in an out-of-round "U" shape to fit inside the existingpipe, then inserted in its out-of-round shape into the existing pipe,and then expanded against the existing pipe under heat and pressure to around condition.

The published EPC Patent Application No. 0,000,576 suggests inserting asemi-rigid plastic tube insert inside an existing pipe. The semi-rigidplastic tube has sufficient hoop strength to withstand all or at leastpart of the external pressures that may be imposed upon it.

a. Repair of Crooked Pipelines and Pipelines with Access at Only One End

Most of the foregoing and other known prior art processes employingrigid or semi-rigid tubes for insertion in an existing underground pipehave a common drawback: because of their rigidity or near rigidity theymust be inserted in straight or nearly straight existing pipelines. Thismeans, for example, with respect to underground sewer lines, such knownprocesses are limited to use in sewer mains because they usually havestraight pipeline sections between manholes. Most if not all of suchknown processes are not suitable for use in repairing the numerousbuilding sewers that extend from the sewer mains to buildings.Frequently such laterals have curves or bends which a rigid orsemi-rigid plastic pipe will not negotiate. Also, such laterals arenormally not accessed by manholes at either end and therefore knownlining or replacement pipe installation methods requiring manhole orother access at both ends are overly expensive. With most knownunderground replacement pipe installation processes, large excavationsmust be made at one end of the lateral to be relined or repaired toprovide room for insertion of the straight rigid plastic replacementpipe. Such a large excavation adjacent to a building serviced by thelateral or at the other end where the lateral intersects the main isoften impractical and usually expensive.

Furthermore, most known processes of relining or repairing existingunderground pipelines require access to the pipeline section to berepaired at both ends of the section. This is not possible with alateral, which by definition intersects a main line at a point that isusually not accessed by a manhole.

For the foregoing reasons, the known underground pipeline relining andrepair processes are simply not applicable to building sewers.

b. Repairing Sewer Mains

Another disadvantage in using known processes of repairing and reliningexisting pipeline sections intersected by building sewer lines usingstraight rigid or semi-rigid tubing is that once the tubing is in placein the existing pipeline section, it is very difficult to locate theexact positions where the service laterals intersect the main pipelineso that access openings can be cut in the replacement tubing to accessthe service laterals. This is especially true if the replacement tubinghas sufficient thickness and therefore sufficient hoop strength toitself withstand typical hydraulic and earth pressures.

For the foregoing reasons, there is a need for improved methods,apparatus and tooling that would enable the repair of existingunderlying pipeline sections, and especially building sewers and otherpipeline sections having bends and curves, and pipeline sections thatcannot be readily accessed from both ends of the pipeline section to berepaired.

Accordingly, primary objectives of the present invention are to providethe following:

1. A new and improved replacement pipeline product for installation inan existing underground conduit that is especially suitable for use inrepairing and replacing existing building sewer lines that are notstraight and main lines intersected by building sewers;

2. A new and improved method of manufacturing a repair and replacementpipeline product especially suitable for installation in existingunderground conduits that are not straight or are intersected by lateralservice lines;

3. A method of installing a new or replacement pipeline section in anexisting underground conduit, and especially one that is not straight orthat is intersected by building sewer lines;

4. Apparatus and tooling for manufacturing a replacement pipelineproduct as aforesaid;

5. Apparatus and tooling for installing a pipeline product as aforesaidin an existing underground conduit, and especially such a conduit thatis not straight or that is intersected by lateral service lines; and

6. Apparatus and tooling for reforming a new or replacementthermoplastic pipe section installed in an existing underground conduit,and especially a building sewer, after the new or replacement pipesection has been inserted in a folded condition, by reforming it to astable rounded shape within the existing conduit.

SUMMARY OF THE INVENTION

The present invention is a new and improved repair and replacementpipeline product especially suited for installation in an existingunderground conduit such as a building sewer with bends and curves, anda series of closely interrelated methods, apparatus and tooling formanufacturing the product, installing the product in an existing conduitwhether straight or curved, and reforming the product to a rounded shapeafter it has been inserted into the existing conduit in a collapsedfolded shape. The product, processes, apparatuses and tooling of thepresent invention are especially intended for use in installing theproduct in building sewers and other existing underground conduitshaving access from only one end of the conduit or having curves or bendsor which are intersected by laterals.

According to one aspect of the invention, a replacement pipeline productis a thermoplastic material such as PVC, extruded and hardened in thefirst instance to a unique folded and flattened shape so that it retainsa folded memory when reheated, so that it can be readily spooled forstorage and use, so that it is of a reduced cross sectional size forready insertion in an existing underground conduit, so that it can beinserted without excavation or damage to the plastic material into deeppipelines through manholes, cleanouts or other small vertical openings,and around sharp bends, and so that, despite its flattened foldedcondition, a hot fluid can be passed through it for reheating its entirelength.

According to another aspect of the invention, the aforesaid plastic pipeproduct is installed in an existing curved lateral, for example, byreheating the plastic pipe to a pliable state, then pulling the hotpliable folded plastic pipe into the existing lateral with a pull cableand either a pulley arrangement anchored temporarily at the intersectionof the lateral and the main, or with a cable winch from the nearestmanhole in the main. The folded installed pipe is then heated throughoutits length by passing a hot fluid through it, plugging or restrictingits leading end, and injecting a fluid, such as air, under pressure intothe other end to reform and expand the pipe to a rounded shape. Then,while continuing to apply internal pressure to the reformed roundedpipe, it is allowed to cool and thereby cure in its rounded shape.

According to another aspect of the invention, various means are providedfor plugging or restricting the leading end of the plastic pipe forenabling the passage of a hot fluid therethrough while folded and yetenabling the expansion and reforming of the folded pipe to a round shapethrough the application of an internal fluid pressure.

According to another aspect of the invention, means are provided forcapping or sealing an inlet end of the folded pipe for enabling internalfluid pressurization of the folded pipe when inserted into an existingunderground pipeline.

According to another aspect of the invention, a unique pulley-and-cabledevice is provided that can be pushed through a service lateral to itsintersection with a main pipeline and temporarily anchored there bymaintaining tension on both ends of the cable. One end of the cable isanchored to the leading end of the folded pipeline to be installed; thenthe opposite end of the cable is pulled to draw the folded plastic pipeinto the existing lateral while in a heated pliable condition.

According to another aspect of the invention, various means are providedfor heating the opposite ends and various other portions of the plasticpipe product for enabling the reworking of selected portions of the pipefor clamping, inserting plugs, or rendering the entire length of thepipe sufficiently pliable for insertion in an existing conduit that isnot straight.

The foregoing and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription which proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of conventional thermoplastic pipe,such as PVC pipe used in accordance with the invention in its expandedrounded condition;

FIG. 2 is a perspective view of the thermoplastic pipe of FIG. 1 andapparatus for reducing the pipe from its round condition to a collapsedand folded condition for storage on a spool;

FIG. 3 is a cross-sectional view of the thermoplastic pipe of FIG. 2after it has been folded as taken along the line 3--3 of FIG. 2;

FIG. 4 is a diagrammatic view showing a process of installing the foldedand spooled thermoplastic pipe of FIGS. 2 and 3 within a sewer main froma manhole, the folded thermoplastic pipe being stored on a roll andbeing reheated for installation in the underground pipe to be rebuilt;

FIG. 5 is a diagrammatic view, in section, showing a detail of apparatusfor expanding the folded thermoplastic pipe of FIGS. 2 and 3 androunding it after it has been inserted in the existing main pipeline asshown in FIG. 4;

FIG. 6 is a diagrammatic view, in section, showing an alternativestructure for expanding and rounding the folded thermoplastic pipe afterits insertion in an existing conduit.

FIG. 7 is a schematic sectional view through a typical building sewerextending from a building serviced to a main sewer line and illustratinga method of installing the thermoplastic pipe in an existing buildingsewer in accordance with the invention;

FIG. 8 is a sectional view through a preferred form of the thermoplasticpipe of FIG. 1 when folded for installation in an existing undergroundconduit;

FIG. 9 is a schematic elevational view of an apparatus for manufacturingthe thermoplastic pipe of FIG. 1 in a folded form as shown in FIG. 8;

FIG. 10 is an elevational view of the calibrator of the apparatus ofFIG. 9 on an enlarged scale as used to manufacture the thermoplasticpipe in the form shown in FIG. 8;

FIG. 11 is an elevational view of a single calibration plate of thecalibrator of FIG. 10 as viewed from the line 11--11 of FIG. 10;

FIG. 12 is a plan view of a folded end portion of the thermoplastic pipeof FIG. 8 with an attached end clamping means for use in pulling thepipe into an existing conduit and for restricting the pipe end to enableinternal pressurization of the pipe for expansion;

FIG. 13 is a sectional view taken along the line 13--13 of FIG. 12

FIG. 14 is a somewhat schematic plan view of a cable-and-pulleyapparatus of the invention, also shown in FIG. 7, for pulling the foldedthermoplastic pipe of FIG. 8 into a service lateral, the apparatus beingshown in its operative position;

FIG. 15 is a view similar to FIG. 14 but with the apparatus of FIG. 14in a collapsed condition for insertion in a service lateral;

FIG. 16 is a somewhat schematic side elevational view of the apparatusof FIGS. 14 and 15;

FIG. 17 is a side elevational view of a plugging tool used in pluggingan end of a length of the thermoplastic pipe shown in FIG. 8 after theend has been rounded, for use in transmitting fluid, heat and fluidpressure to the interior of the thermoplastic pipe;

FIG. 18 is a leading end elevational view of the tool of FIG. 17;

FIG. 19 is a view of an end of the thermoplastic pipe with the pluggingtool of FIGS. 17 and 18 inserted in the pipe and clamped in place with achain clamping means;

FIG. 20 is a view of the chain clamping means of FIG. 19 before itsapplication to the pipe and plug of FIG. 19;

FIG. 21 is a cross-sectional view taken along the line 21--21 of FIG. 19showing the chain clamping tool of FIGS. 19 and 20 clamping thethermoplastic pipe end to the plugging tool of FIGS. 17-19;

FIG. 22 is a somewhat schematic longitudinal sectional view through aleading end portion of the thermoplastic pipe of FIG. 8 with the endclamp of FIGS. 12 and 13 applied to the pipe end and with the remainderof the pipe expanded and rounded, and with a cutting tool in accordancewith the invention inserted in the rounding pipe end portion forsevering the clamped end from the remainder of the pipe;

FIG. 23 is a sectional view of the pipe and cutting tool of FIG. 22taken along the line 23--23 of FIG. 22;

FIG. 24 is a somewhat schematic side elevational view of an end heaterapparatus used in heating an end portion of the thermoplastic pipe forreworking the end portion, the heater tool being shown installed on afolded end portion of the thermoplastic pipe of FIG. 8;

FIG. 25 is a perspective view of an inflatable end plugging tool used inplugging or restricting the end portion of the thermoplastic pipeinstead of the end clamping means of FIGS. 12 and 13 to enable expansionand rounding of the folded thermoplastic pipe;

FIG. 26 is a foreshortened elevational view, partly in section, of theinflatable pipe of FIG. 25;

FIG. 27 is a schematic view illustrating installation of the inflatableplugging tool of FIGS. 25 and 26 in the thermoplastic pipe when in anexpanded and rounded condition;

FIG. 28 is a schematic view similar to FIG. 27 but showing the pipe ofFIG. 27 after it has been refolded with the inflatable plug in adeflated condition inside;

FIG. 29 is a schematic view illustrating the use of the inflatableplugging tool of FIGS. 25 and 26 during installation of thethermoplastic pipe in a service lateral;

FIG. 30 is a schematic view illustrating another use of the inflatableplugging tool of FIGS. 25 and 26;

FIG. 31 is a schematic view further illustrating the use of theinflatable plugging tool of FIGS. 25 and 26 in accordance with theprocess illustrated in FIG. 30;

FIG. 32 is a schematic view illustrating still another use of theinflatable plugging tool of FIGS. 25 and 26 to expand and round thefolded thermoplastic pipe after it has been inserted into an existingunderground conduit;

FIG. 33 is a schematic view of a main pipeline section and anintersecting service lateral pipeline illustrating an alternative methodof pulling the thermoplastic pipe of FIG. 8 into a service lateral to berepaired;

FIG. 34 is a schematic view of an end portion of the foldedthermoplastic pipe of FIG. 8 illustrating one method of releasing thepull cable from the leading end of the pipe after it has been insertedin an underground conduit;

FIG. 35 is a schematic view similar to FIG. 34 illustrating stillanother method of releasing the pull cable from the thermoplastic pipeafter it has been inserted into an existing underground conduit;

FIG. 36 is a sectional view through the intersection of a main pipelineand a service lateral pipeline the thermoplastic pipe of FIG. 8 has beeninstalled and expanded within the main pipeline to be repaired, andillustrating a method of locating and cutting an opening through thenewly installed thermoplastic pipe to reopen communication between theservice lateral and the main pipeline;

FIG. 37 is a schematic side elevational view illustrating and method andapparatus for folding a thermoplastic pipe that has been manufacturedround, for insertion in an existing underground conduit;

FIGS. 38A-E are schematic sectional views taken, respectively, along thelines 38A--38A through 38E--38E of FIG. 37;

FIG. 39 is a somewhat schematic side elevational view of a releasableend clamp and attached pull cable and release line, for use in clampingthe leading end of the folded pipe of FIG. 8 during its installation;

FIG. 40 is a top plan view of the end clamp of FIG. 39; and

FIG. 41 is a top plan view of the release wedge portion of the clamp ofFIG. 39.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Repair of Sewer Mains andthe Like

With reference first to FIG. 1, the numeral 10 designates a type of pipewhich is used to rebuild, repair or replace underground pipelinesections such as sewer pipes or the like according to the presentinvention. A characteristic of the pipe 10 is that it is formed of athermoplastic material such as PVC, and more particularly a materialthat is normally rigid and thick-walled so as to have sufficient hoopstrength to withstand external earth and hydraulic pressures to which itmight be exposed when underground. Yet such thermoplastic pipe be can bemade pliable upon heating to temperatures of, for example, 200° F. orabove in the case of PVC pipe. A characteristic of the pipe is that itis structurally rigid at typical ambient above-ground and undergroundtemperatures but becomes pliable and workable to various shapes whenheated or reheated. Another characteristic of such thermoplasticmaterial is that it has a memory; than is, if it is manufactured in aparticular shape such as a rounded tubular shape and then later heatedand flattened or folded and then cooled to cure in its folded shape, andthen reheated without restraint, it will tend to return to its originalrounded tubular shape. Conversely, if the pipe is manufactured initiallyin, for example, a collapsed and folded shape, as shown for example inFIGS. 3 and 8, then later heated and expanded under internal pressure toa rounded shape and then cooled and cured in its rounded shape, it willtend to return to its original folded shape if subsequently reheatedwithout restraint. This memory aspect of the thermoplastic pipe is usedto advantage in certain aspects of the present invention.

A conventional and readily available pipe of the type useful inpracticing the present invention is a polyvinyl chloride (PVC) pipe withstandard dimension ratios (outside diameter/wall thickness) in the rangeof 13 to 65 presently available for underground pipelines such as drainlines, water lines, etc.

Although in the most preferred embodiment of the present invention thethermoplastic pipe is manufactured in a folded shape as shown in FIG. 8in the manner described with respect to the apparatus of FIGS. 9-11, atleast certain aspects of the invention can also be practiced using athermoplastic pipe manufactured in a tubular or round shape. FIG. 2illustrates apparatus 11 for reshaping the conventional PVC pipe 10 thathas been manufactured in a round shape. FIG. 3 illustrates across-section of the pipe 10 after it has been reshaped by flatteningand folding using the apparatus of FIG. 2. More particularly, the PVCpipe 10 is heated in any conventional manner, such as by a heating means11a, which may be a thermostatically controlled steam box or a housingcontaining thermostatically controlled electric heating elements. Bypassing the original round pipe 10 through the heating box 11a, the pipeis heated to a temperature sufficient to make the pipe plastic orpliable. It is then flattened or preferably folded, in a foldingapparatus 11 to reduce its overall cross-sectional dimension so that itis capable of being pulled readily into an underground conduit havingthe same or only slightly larger inside diameter than the originaloutside diameter of the thermoplastic pipe. The thermoplastic pipe ofreduced folded dimension is illustrated at 10a in FIG. 3.

Although the unit 11 in FIG. 2 illustrates schematically a pipe foldingmeans, a practical pipe folding apparatus and method are illustrated inmore detail with respect to the apparatus of FIGS. 37 and 38A-E. Thereit will be seen that the round pipe 10, after passing through the heater11a, is first flattened by a pair of opposed flattening rollers 60, 61and then passed beneath a folding wheel 62 while supported progressivelyby three different sets of folding rollers 63, 64, 65. The pair offolding rollers 63 are arranged in cooperation with folding wheel 62 tobegin folding pipe 10 into a U shape. Then the three folding rollers 64continue the folding process by being arranged in a semi-U shape forcooperation with folding wheel 62. Finally, the set of four foldingrollers 65 are arranged in a U shape for cooperation with the foldingwheel 62 to complete the folding of pipe 10 into a U shape. Thereafterthe folded pipe is passed through a restraining form 66 while it iscooled to cure the pipe in its U shape. From form 66 the folded pipe canbe either stored in predetermined lengths or passed through a steam tubeto be reheated and made pliable for insertion directly into an existingconduit.

Alternatively, after the flattening process and before folding, the pipecan be spooled in its flat condition in the hot box 18 shown in FIG. 4.Then the flat, spooled pipe can be reheated in the hot box at the jobsite, and then pulled from the hot box and folded as previouslydescribed just before insertion into the pipe to be rebuilt.

In some applications it may also be possible to install thethermoplastic pipe into an existing pipe in a flattened condition,particularly if the thermoplastic pipe in its rounded condition is ofsubstantially smaller outside diameter than the inside diameter of thepipeline to be repaired. However, under most conditions, it is preferredthat the thermoplastic pipe be installed in an existing pipeline in alongitudinally folded form as shown in either FIG. 3, FIG. 8, or in FIG.38E. However, of all the folded forms, the form of FIG. 8 is preferredfor reasons explained below.

As previously mentioned, the thermoplastic pipe when manufactured in around shape has a memory tending to return it to its round shape when itis reheated after folding. Thus when if it is necessary to reheat thefolded pipe to rended it pliable for installation in an existingpipeline, the pipe will tend to return to its round shape, perhapsprematurely, unless restrained. It is for this reason, primarily, thatit is preferred that the thermoplastic pipe be manufactured in the firstinstance in a desired folded shape. Then when the folded pipe isreheated to make it pliable for insertion in an existing pipeline, thepipe will retain its folded shape until fully inserted into the existingpipeline and ready for reforming into a round shape.

Regardless of whether the thermoplastic pipe is manufactured in a roundor folded shape, the pipe should be in a folded shape when it is readyfor insertion in the existing conduit. It is also preferred that thethermoplastic pipe be spooled while heated and therefore made pliable ona storage spool such as spool 12 shown in FIG. 4.

The spool 12 of folded thermoplastic pipe is stored in a housing or "hotbox" 18 equipped with a thermostatically controlled heater 24 forheating the interior of the hot box and thus the spool 12 to render thefolded pipe material 10a pliable when desired. Preferably hot box 18 isalso equipped with an air circulation system 19 to prevent heatstratification within the hot box, and thereby to ensure that the spoolof folded pipe will be uniformly heated. Hot box 18 is preferablymounted for portability and is shown mounted on the flat bed of a truck20 for transportation to a job site. A smaller form of the hot box maybe wheel-mounted and manually moved for use in the servicing smallinaccessible pipelines such as building sewers. In either case, eitherpower operated or manual means are provided for rotating the spool 12for winding material on the spool or unwinding it from the spool. Hotbox 18 is equipped with an access door 21 and may also be equipped witha downspout 22 and a roller 23 for facilitating insertion of the foldedthermoplastic pipe into an underground pipeline through a verticalaccess opening such as the manhole 16 of the existing sewer main 14.

Method of Repairing Sewer Main

According to one aspect of the invention, the hot box 18 is transportedto an opening at a job site, such as the manhole 16, at an undergroundpipe section such as the sewer main 14 to be repaired. The end of thereduced pipe 10a is connected to a pull line 26 made available from anadjacent opening in the existing pipeline, such as another manhole (notshown), and connected by clamp means 28 to the free or leading end ofthe new pipe. The new pipe is made pliable by heating spool 12 in thehot box 18 via heater 24. The pull line 26 is then activated by, forexample, a winch at the next manhole downstream from manhole 16 to pullthe pliable folded pipe 10a from spool 12 through spout 22 and aboutspout roller 23 into existing pipe 14 to the next manhole. Afterinserting the folded new pipe, it is heated and expanded to a round orsubstantially round form to provide a pipe which will set up into athick-walled, rigid form having sufficient hoop strength to withstandexternal hydraulic and earth pressures.

FIG. 5 illustrates one manner of expanding the reduced dimension pipeafter it has been pulled into the original pipe to be rebuilt orreplaced. According to such method, a pair of plugs 30 and 32 areinserted in the opposite ends of the folded pipe when at least the endsare in a heated pliable condition. The plug 30 is installed at atrailing end of the new pipe section which is at the insertion end ofthe existing pipeline. The plug 32 is installed at the leading orpull-line end of the new pipe after disconnection of the pull line. Eachof plugs 30 and 32 is equipped with peripheral expanding gasket members34 arranged for releasible sealing engagement with the original pipe 14and the new pipe 10a. Gasket members 34 are inflated via pressure lines36, such as air pressure lines, leading to control means (not shown)above ground. Plug 30 has an inlet conduit 38 therethrough forintroducing into the new pipe an expanding medium such as live steam orhot water. Such conduit is equipped with a suitable control valve 40 aswell as a pressure gage 42 and a relief valve 44. Plug 32 has adischarge conduit 46 communicating with the area between the two plugsand suitably valved at 48.

The newly installed folded pipe, with the plugs inserted at its oppositeends, is then internally heated by passing live steam through the smallpassages provided at the folds of the new pipe evident in FIG. 8. Valve48 at the downstream end is open so that the entire length of the newpipe is heated. Valve 48 is then closed while steam under pressurecontinues to be introduced through plug 30 to pressurize the foldedpipe, causing it to reform and expand to a rounded shape. If the newpipe is manufactured folded, it should be cooled or allowed to coolafter attaining its round shape while maintaining internal pressure,such as cool air pressure, so that the pipe cures in its round shape.This last step is not necessary if the pipe is manufactured in a roundshape unless the pipe is expanded or stretched beyond its originaldiameter during the reforming process.

If no internal passages are provided in the folded new pipe such aswould be the case if the new pipe is folded absolutely flat as shown inFIG. 3, the new pipe would have to be heated externally, such as bypassing live steam through the existing pipe, before plugs 30 and 32 areinserted into the ends of the new pipe. Then with the new pipe heatedthroughout its length, plugs 30 and 32 could be easily inserted into itsopposite ends, valve 48 would be closed, and live steam or hot waterwould be introduced through plug 30 to expand the folded pipe and reformit into a round shape.

FIG. 6 shows another type of apparatus for expanding the reduced pipe.Such apparatus comprises a mandrel 50 having heating means 52 thereincapable of heating the new pipe into a pliable state. Mandrel 52 isconnected to a pull cable 54 or other means for drawing it through theoriginal pipe. Upon proper heating of the mandrel and throughapplication of tension to the pull cable, the mandrel is pulled throughthe original pipe, expanding the new pipe to the desired diameter.Obviously with this method, pull cable 54 would be inserted into the newpipe before the new pipe is folded for insertion into the existingpipeline.

A third method of heating, rounding and expanding the new pipe involvesflushing hot water or steam down the existing pipe to be repairedalongside the installed but still folded new pipe until the desiredtemperature is achieved at the downstream end. Then the new pipe ispressurized with hot water or steam and expanded under pressure to around shape and to the desired diameter.

EXAMPLE

In a specific pipe reconstruction process, conventional PVC pipe isobtained which is one-half inch, plus or minus, smaller in outsidediameter than the inside diameter of the pipe to be rebuilt. The PVCpipe has standard dimension ratios of wall thickness to outside diameteras noted previously. The PVC tubing is heated to at least 200°-210° F.and reduced to the shape shown in FIG. 3, FIG. 8 or FIG. 38E. The foldedpipe is then stored on large spools so that it can be trucked to the jobsite. During installation in an existing pipe or conduit underground,the new pipe is again heated, preferably in hot box 18, so as to be madepliable and capable of being pulled readily generally vertically downthrough a deep manhole and then generally horizontally through theexisting conduit. Once installed in the existing conduit section thefolded pipe is plugged, heated and rounded. If desired it may also beexpanded beyond its original or design rounded diameter to fit snuglyagainst the existing pipeline section.

Method of Locating Building Sewer Connections

An advantage of expanding the newly installed thermoplastic pipe beyondits original design diameter is illustrated with respect to FIG. 36,where the existing pipeline section to be repaired is intersected by atleast one building sewer line or other service lateral. In FIG. 36, themain pipeline 70 is intersected at 72 by a service lateral 74 such as abuilding sewer line. When the new thermoplastic pipe is installed in themain 70 and rounded and expanded or stretched beyond its originalrounded design diameter to snugly engage the inside wall of existingmain 70, a bulge or dimple 76 is formed at the opening or intersection72 of the service lateral into the main. This bulge 76 in effect is anindicator of the precise location of the opening of the service lateralinto the main. By passing a television camera through the main, theexact location of the bulge or dimple, and thus the service lateralopening, can be determined. Thereafter a remotely controlled cuttingtool 78 can be passed along the main to the exact location of the bulgeand used to cut the bulge 76 from the new pipe 80, thereby reopeningaccess of the service lateral 74 to the main.

Rounding and expanding, or stretching, of the newly installedthermoplastic pipe is achieved by the methods previously described or asdescribed hereinafter with respect to additional embodiments.

Preferred Form of Folded Pipe

Although the flattened and folded thermoplastic pipes of FIGS. 3 and 38Eare suitable for use in the installation processes described, thepreferred form of such folded pipe is shown in FIG. 8. The thermoplasticpipe 10 of FIG. 8 is manufactured in substantially the folded formshown. It is generally a collapsed tube folded along a generally curvedbulbous longitudinal fold 82 into a pair of overlying legs, including along leg 83 and a shorter leg 84. The long leg 83 terminates at a curvedor bulbous free end 85 so as to define a small longitudinal passage 86through the folded pipe. The shorter leg 84 also terminates in a curvedor bulbous free end 87 which also defines a longitudinal passage 88through the pipe. Furthermore the gently folded portion 82 defines apassage 89 along the interior of the fold from one end of the pipe tothe other.

The bulbous fold and leg ends as described are important in preventingthe folded portions of the pipe from splitting when folded, which mightotherwise be the case if the pipe is folded flat in the manner shown inFIG. 3, especially if the pipe is thick-walled. Passages 86, 88 and 89are also important in enabling steam or other hot fluid to passfull-length through the folded pipe for reheating and thus reworkingafter the folded pipe is installed in an existing underground conduit.Without such access to the interior of the folds, reheating would be along, slow process and very difficult to achieve.

The folded form of pipe of FIG. 8 is especially suitable for use asreplacement pipe in the repair of building sewers such as a buildingsewer line 90 shown in FIG. 7 leading from an intersection 92 with amain pipeline 94 into a building 96 to be serviced. Installation of areplacement pipe in such building sewer lines presents special problemsbecause of the nature of such lines. First, such laterals presentdifficult access problems because they often run under lawns, trees andshrubs and are not accessed by manholes. Digging up the existing lateralin need of repair would thus be very expensive. In inserting a newlateral into an existing lateral underground, access is usuallypractical only from a single small vertical excavation adjacent to thebuilding, as indicated at 98 in FIG. 7. Such an exacavation leaveslittle room for maneuvering or for a large amount of equipment.

Second, building sewers are usually of much smaller diameter than mainsand frequently have sharp curves or bends, unlike mains which areusually straight from manhole to manhole. For example, the buildingsewer 90 has a bend at 100, making it impossible to insert into theexisting lateral a straight rigid pipe. In FIG. 7 the building sewer 90,accessed by the vertical excavation 98 adjacent to building 96, extendsbeneath a lawn 102 to the main 94 at a substantial depth below a street104. The processes and apparatuses about to be described areparticularly suited for solving the unique problems of installing areplacement lateral pipe in an existing lateral pipe underground from asingle small, generally vertical access opening. Such methods andapparatuses utilize the manufactured form of folded thermoplastic pipeshown in FIG. 8.

Method and Apparatus for Manufacturing Thermoplastic Pipe in Folded Form

Referring to FIGS. 9, 10 and 11, the folded thermoplastic pipe of FIG. 8is manufactured using a conventional plastic pipe extruder 106 extrudinginto a vacuum box 108. Puller means 110, comprising a series of opposedpinch rolls 111, 112, downstream of the vacuum box, pulls the extrudedand formed material from the vacuum box under tension and feeds it intoa steam tube 114 for reheating to a pliable condition so that theresulting folded pipe can be wound in its folded form on a storage spool116 which would typically be located in the hot box 18 of FIG. 4.

A die 118 and pin 120 are located at the extruder outlet. There is a gap121 of between about 12 and 24 inches between the downstream end of thedie 118 and the inlet to the vacuum box 108.

The vacuum box is divided internally by partitions 122, 123 into threesections. All three sections are filled with water to a level 124 withinthe box. The first or upstream section of the box is connected to asource 125 of vacuum. Although the entire vacuum box is under a negativepressure because of such connection, a maximum negative pressure is inthe upstream section of the box. Calibrator means 126 are provided inthe first section of the vacuum box. The calibrator means forms andmaintains the extruded plastic material in its desired folded shape asthe material is cooled and therefore cured. The water within the vacuumbox serves the cooling function, and the vacuum supplied to the boxcooperates with the calibration means to maintain the plastic materialin its desired folded form until, through cooling, it is capable ofmaintaining such form without restraint.

Referring especially to FIGS. 10 and 11, the calibration means includesa series of calibration places 128 arranged in spaced-apart relationshipand assembled together by assembly rods 130 and spaced apart by spacers132 between plates on the rods. The rods are threaded at their oppositeends and secured by nuts 134. The calibration plates 128 closer to theinlet end of the calibrator are spaced more closely together than thosefurther downstream because of the greater plasticity and flowability ofthe plastic at the inlet end portion and therefore the greater need tomaintain the shape of the extrusion in that portion of the calibrator.Optionally, the calibrator also includes a central tube 136 withorifices 137 for transmitting cooling water to and between the platesfor more rapid cooling of the plastic material.

Referring to FIG. 11, each calibration plate 128 includes a precisioncut opening 138 of the exact outline shape and outer size of the foldedpipe formed and maintained in the calibration plates. Each plate 128 ofthe calibrator has exactly the same size and shape of opening. ComparingFIGS. 8 and 11, it will be noted that the opening 138 of the calibrationplate includes a short leg 138a corresponding to the short leg 84 of thefolded pipe and a long leg 138b corresponding to the long leg 83 of thepipe as well as a rounded fold portion 138c corresponding to thelongitudinal rounded fold 82 of the pipe.

In manufacturing the pipe of FIG. 8, raw plastic mix such as polyvinylchloride is fed into the extruder 106 through an infeed funnel 107 wherethe material is heated to a high temperature of, for example, about 360°F. and then extruded through the die 118 where the very hot plasticmaterial encounters the pin 120. The die and pin are sized to form theplastic Into the desired final size and shape of the tube desired. Theplastic material is fed across the gap 121 into the first section of thevacuum box 108 and through the calibrator plates. The plates form andmaintain the plastic material in the shape and size determined by thecalibration plate openings 138.

When the plastic material first enters the calibrator it is very hot andrather fluid, and therefore the calibration plates 128 are very closetogether at this point to maintain the desired shape. The vacuum withinthe box holds the plastic against the outer periphery of the opening 138as the cooling water cools the plastic material. If desired, compressedair injected from a source 140 into pin 120 can be passed down throughthe interior passages 86, 88, 89 of the folded plastic form to ensurethat the plastic does not completely collapse and to maintain thetubular form of the folded pipe. By the time the plastic materialreaches the downstream end of calibrator 126, it is cooled substantiallyand is capable of maintaining own shape under tension induced by pullingrolls 110. Such rolls pull the folded plastic from the vacuum box in acontinuous strip. From the calibration plates, the strip travels throughthe second and third chambers of the vacuum box, where it isprogressively cured. By the time the strip 10 leaves the vacuum box itis cool, rigid and substantially in the form shown in FIG. 8. Puller110, by pulling the strip or stream of material from the extruder undertension, controls the wall thickness and other dimensional parameters ofthe folded pipe.

From puller 110 the folded strip is fed through steam tube 114 intowhich a source of steam 115 is fed through an inlet opening 117 toreheat the strip to a pliable condition so that it can be spooled onstorage spool 116.

The number and spacing of calibrator plates used in the calibrator is afunction of the extrusion speed as determined by the puller and of thedesired wall thickness of the finished pipe.

As previously mentioned, the spool 116 of stored folded pipe 10 may beinstalled in the hot box 18 shown in FIG. 4 for transportation to anduse at a job site.

Method, Apparatus and Tooling for Installing Thermoplastic Pipe inLateral

FIG. 7 not only illustrates a sewer lateral as previously described, butalso a method, apparatus and tooling for inserting the foldedthermoplastic pipe at FIG. 8 into the lateral. First, a verticalexcavation 98 must be dug, preferably as close to building 96 servicedby the lateral 90 as possible to break through and provide access toexisting lateral 90.

Then the length of the lateral to be repaired or replaced can bedetermined by inserting a flexible fiberglass rod into the lateral atthe excavation and feeding the rod through the lateral until itintersects main 94. When this occurs, the length of the rod within thelateral can be marked at the access opening and then the rod withdrawnand measured to determine the length of plastic pipe 10 needed for thejob. When the lengths of a series of laterals to be repaired is known,the folded pipe 10 can be precut to correspond with such lengths, eitherat the manufacturing plant or at some other location remote from the jobsite. Then such precut lengths can be transported to the job sites forinstallation.

Alternatively, the lengths required can be cut at the job site from thespool 116 or 12 (FIG. 4) within the hot box 18 transported to the jobsite. If the excavations for the laterals to be repaired are notaccessible to the truck 20 on which the hot box 18 is mounted, thenecessary length of plastic pipe 10 can be stored on other, smallerspools within smaller wheel-mounted hot boxes (not shown) wheeled to therespective excavations. A smaller "mini hot box" 140 is shown in FIG. 7enclosing a spool 142 of folded pipe 10.

Alternatively, rather than premeasuring and precutting the requiredlengths of folded plastic pipe 10 to lengths corresponding to thelengths of the laterals to be repaired, the folded pipe 10 can be simplyheated within the hot box 140 and fed into the existing lateral untilthe new folded pipe reaches the intersection with main 94, and then cutoff at the spool.

Also, if the folded plastic pipe 10 is precut to length at the factory,it can be transported in its precut lengths to the various job sites andthere heated for insertion into the existing lateral in a steam tubelike the steam tube 114 shown In FIG. 9. The steam tube may be made ofcanvas or metal or equivalent materials, with flexible fabric orequivalent ends which can be tied around the folded plastic pipe to keepthe steam inside the steam tube. Such tubes are lightweight for easytransportation to a job site and can be 20 feet long or longer. Forfield use, a canvas steam tube is preferred over the metal tube becauseof weight considerations.

If the sewer lateral is straight and its access opening at theexcavation close enough to the surface, or the excavation large enough,it may be possible to insert the necessary length of folded plastic pipe10 Into the existing lateral simply by pushing the new pipe into theexisting pipe until the leading end reaches the main. However,oftentimes this will not be possible because of the necessity of the newpipe to negotiate a bend at the excavation or along the lateral, orboth. In such cases, it is necessary to heat the normally rigid foldedplastic pipe to render it longitudinally pliable to negotiate the bendsand to pull the new folded pipe Into the lateral rather than push it.Pulling the flexible folded plastic pipe into the existing lateral,without an access opening at the main end of the lateral, presentsspecial problems addressed by the present invention.

Pulling the New Lateral into the Existing Lateral from the AccessOpening

One method of inserting the new lateral into the existing lateral bypulling involves the use of a pull cable attached to the leading end ofthe new lateral. The cable passes about a pulley at the connection ofthe lateral to the main, and then leads back to the entrance to thelateral. By applying a pulling force to the pull cable from the accessopening at the excavation 98, the new pipe can be pulled through thefull length of the existing lateral. This method involves the use ofspecial tooling.

First the leading end of the new lateral must be clamped closed torestrict the size of the through passages 86, 88, 89 as shown in FIG. 8to enable internal pressurization of the folded Dips after it isinserted into the existing lateral while still enabling hot fluid topass through the folded pipe so that it can be heated throughout itslength and thereby rendered pliable for expansion and rounding. Toaccomplish this restriction and end clamping, an end clamping means asshown in FIGS. 12 and 13 is used. A side view of the end clamping meansis also shown in FIG. 22. With reference to these three FIGS., the endclamping means 144 includes a pair of rigid metal plates. The platesinclude a top plate 145 and an opposed bottom plate 146. Both plateshave fowardly projecting nose portions 147 with aligned pull cableconnecting holes 148 extending therethrough. Another pair of alignedholes 149 extend through the bottom and top plates rearwardly of thecable hole 148 for receiving a clamping bolt 150. Bolt 150 also extendsthrough aligned drilled holes 151 through the folded plastic pipe 10.

To install end clamp 144 on the leading end of folded plastic pipe 10the leading end of the pipe is heated to render it pliable in, forexample, an end heater 152 shown in FIG. 24. End heater 152 includes athin-walled rigid pipe 154 closed at one end by an end plate 156 havinga central inlet port 157 with a steam hose connection 158. The oppositeend of the heater includes a flexible canvas or other suitable fabricwrap 160 banded to pipe 154 at connecting band 162. The free end of wrap160 can be tied or banded about the folded plastic pipe 10 in such a waythat steam is allowed to escape at the connection 164 of the wrap withthe pipe so that the entire end portion of the pipe is heated to adesired temperature upon injection of steam into the pipe throughconnection 158. The length of pipe 152 may be in approximately two feetfor most purposes although it can be longer and shorter depending on theapplication.

After the leading end of pipe 10 is rendered pliable, the plates of endclamp 144 are applied to the end of the pipe, and bolt 150 is extendedthrough bolt holes 151 and tightened so that the opposed plates 145, 146squeeze an intermediate portion of the folded pipe to a more flattenedcondition to reduce the size of passages 86, 87, 89 at the end of thefolded pipe. It should be noted that the widths of clamping plates 145,146 are substantially narrower than the overall width of the folded pipe10 so that passages 89 at the fold and 86 at the end of the long leg donot become completely closed upon application of eloping force to thefolded pipe. Thus when the clamp is applied, fluid can still passcompletely through the clamped end of the pipe, yet the passages aresmall enough such that a buildup of internal pressure within the foldedpipe can be achieved to expand and round the pipe.

The described end heater is also useful for other purposes as will soonbecome apparent from the following description.

Releasable End Clamp

Another form of end clamp, which can be used instead of end clamp 144,is a releasable end clamp 250 shown in FIGS. 39-41. Clamp 144 has thedisadvantage of not being removable from the leading end of pipe 10 wheninserted into a blind conduit without cutting off the clamped end of theconduit using a special remotely activated cutting tool as shown inFIGS. 22 and 23 and described hereinafter. However, releasable end clamp250 can be remotely released from the clamped end of the new pipe whendesired and pulled by cable from the existing conduit.

Releasable clamp 250 includes an upper paw 252 pivoted at 254 to a lowerjaw 256. Lower jaw 256 includes a leading end projection 258 with a pullcable hole 260 extending therethrough for attaching a pull cable 262.Jaws 252, 256 have gripping ends 263, 264 for gripping and compressingwhen hot and pliable, a leading end portion 266 of folded plastic pipe10.

A bolt 268 extends through a large opening 270, larger than the head 269of the bolt, and through an aligned smaller bolt hole 272 in lower jaw256. Bolt hole 272 is smaller than the nut 273 and head 269 of bolt 268.A bifurcated release wedge member 276 has parallel arms 277, 278defining a slot 280 and joined to a vertically wedge-shaped body 282. Aflexible release cable or cord 284 is attached to the body 282 bypassing it through body hole 286.

Wedge member 276 is designed to be wedged between the head 269 of bolt268 and the upper surface of upper jaw 252 with arms 277, 278 extendingbeneath the head and slot 280 receiving the shank of the bolt. Thus bolthead 269 is drawn against arams 277, 278, rather than through largeupper jaw opening 270, when the bolt is tightened to clamp jaw ends263,264 against pipe 10.

To release the clamp from the new pipe after the pipe has been pulledinto the existing sewer lateral using pull cable 262, and after the newpipe has been rounded except for the clamped end, release cable 284 ispulled. This pulls wedge member 250 from beneath bolt head 269 (or nut273 if the nut end of the bolt is above the top jaw), allowing the bolthead to drop through the large opening 270 in the upper jaw 256, andthereby allowing the jaws to open to release the pipe end. The wedgemember and the clamp can be pulled from the lateral or main using theirrespective pull cables.

Pulley-and-Cable Frog

Another tool used in pulling the new folded lateral into the existinglateral from the access opening 98 is a pulley-and-cable means referredto as a "frog", as shown in FIGS. 14-16. The frog 152 includes a cablepulley wheel 154 rotatably mounted within a pulley housing 156 on anaxle 157. Attached to opposite sides of the open rear end of the pulleyhousing are a pair of angular legs 158. Each leg includes a forward legsection 158a and an integral rearward or trailing leg section 158b.Trailing rearward from the trailing leg sections 158b are a pair offlexible steel leg guide bands 160 curled inward at their rear ends 161.The pivot connections 162 of the legs 158 to housing 156 arespring-loaded to urge the legs outward as shown in FIG. 14. However, thelegs can be pivoted inward to the positions shown in FIG. 15 to allowthe legs and thus the entire assembly to travel through the lateral.

A pair of generally triangular-shaped arms 164 are pivoted to theJunctures of forward and rearward leg sections 158a, 158b atspring-loaded pivot connections 166. The spring-loaded connections 166urge the arms 164 to their extended positions shown in FIG. 14 normal torearward leg sections 158b when they are in their extended positions ofFIG. 14. However, the arms 164 may be collapsed against spring pressureto their collapsed positions shown in FIG. 15, again to allow the frogto travel through a lateral to its destination. A pull cable 168, withboth ends leading back to access opening 98, is trained about pulleywheel 154.

With its pull cable 168 attached, but with both ends of the cableleading back to access opening 98, the frog is inserted into theexisting lateral and pushed through it using a flexible fiberglass pushred (not shown). when the frog reaches the intersection of the lateralwith the main, and with the housing 156 and its connected pulley pushedinto the main, and also with the forward legs 158a entering the main,arms 164 spring outward from their positions shown in FIG. 15 to theiropen positions shown in FIG. 14. In the open position of the legs,rearward leg sections 158b and their connected leg bands 160 pressagainst the inner wall of the existing lateral. At this point, both endsof pull cable 168 are pulled to anchor the frog firmly to the junctionof the lateral and main.

While continuing to apply tension to the pull cable to keep the froganchored in place, one end of the pull cable is attached to end clamp144 (FIGS. 12-13) or releasable end clamp 250 (FIGS. 39-41). The otherend of the cable, still at access opening 98, is pulled, pulling theheated, pliable folded plastic pipe 10 through the lateral and aroundbend 100 until the leading end of the folded pipe 10 reaches theintersection of the lateral and main at frog 152. Pulling force can beapplied to the cable 168 to accomplish this either by hand or by using ahand-or power-operated winch 170 (FIG. 7) at access opening 98. Becauseof the triangular shape of arms 164, pulling tension applied to cable168 prevents the frog from flipping up or down.

After the new folded plastic pipe reaches the frog in the main, thecable connection to the pipe end clamp is released, and an end of thecable is pulled through the pulley, dropping the frog into the main. Thecable is then pulled out of the service line from the entrance opening,and the frog can be retrieved from the main at a later time usingconventional retrieval methods. At this point the folded plastic pipe 10is fully inserted into the lateral to be repaired, with its clampedleading end at the main. The folded plastic pipe is now ready to bereheated and expanded to a rounded shape in the existing servicelateral.

Before discussing the expansion and rounding process as applied toservice laterals, mention should be made of the method and means forreleasing pull cable 168 from end clamp 144 so that the cable can bepulled through the frog. This can be accomplished in several ways asshown, for example, in FIGS. 34 and 35.

FIG. 34 illustrates what is referred to as a break-away cable release.In this method, a "slack" end 168a of the pull cable 168 is attached toa relatively low-strength breakable string or cable 172 which is in turntaped at 173 to a leading portion of folded pipe 10 to be inserted intothe existing lateral. From its slack end, pull cable 168 is looselylooped through cable hole 148 in the end clamp as indicated by looseloops 168b, 168c, and then trained through the pulley of the frog. Thepulling end of the cable remains at the access opening to the lateral.If an end clamp is not used, the cable hole 148 may be drilled directlythrough the folded leading end of the plastic pipe. As the winch at theaccess opening pulls the cable through the frog to winch the folded newpipe into the existing lateral, string 172 holds moderate tension on theslack end 168a of the cable. When the leading end of the folded new pipereaches the frog, the pulling end of the cable is sharply jerked,breaking string 172 and releasing the slack end 168a of the cablethrough cable hole 148 so that the cable can be retrieved.

FIG. 35 illustrates a similar cable release method referred to as thehand-held cable release. In this method, the slack end portion of cable168 is again looped twice loosely though the cable hole 148 at theleading end of the folded new pipe 10 to form the double loops 168b,168c. Then the pull cable 168 is lead through the existing lateral 90 tothe frog and back to the entrance opening. The slack portion 168a of thecable must be longer than the length of the new pipe 10 to be inserted.As the winch pulls the new pipe into the existing lateral, a moderatetension is held on slack end 168a of the cable, allowing the folded newpipe to be pulled into the lateral. When the new pipe is properlyinserted in the existing lateral, slack end 168a of the cable isreleased at the entrance opening, allowing it to be pulled free from theleading end of the newly inserted pipe through cable opening 148.

Method and Apparatus for Expanding and Rounding Folded Pipe withinLateral

With the folded new pipe in place within the existing lateral, it isready to be expanded and rounded to replace the existing lateral as afunctioning service lateral. At this point the leading end of folded newpipe 10 is already restricted by an end clamp 144 or 250 so that thefolded pipe can be pressurized internally by fluid and yet allow hotsteam or other fluid to pass through it. This enables the entireinternal length of the folded pipe to be heated to a pliable conditionfor expansion. Of course, at this point, the trailing end of the newlyinserted folded pipe is also capped to enable the introduction of hotsteam or other fluid into the pipe for heating and expansion. Such acapping means, or plug, is shown in FIGS. 17-21.

A generally conically-shaped plug, referred to as a "torpedo plug" 176includes a generally conical leading portion 178 having an orifice 180at its leading end. Conical portion 178 extends rearwardly to a shortcylindrical portion 182 which is capped by a rear end plate 184. Plate184 includes an inlet port 186 and a hose connection 188 for coupling asteam or hot water supply hose so that hot fluids under pressure can beintroduced into the interior of the folded pipe. Other hose connectionscan also be provided through end plate 184, such as an air hoseconnection, for expanding the pipe using air pressure or maintaining airpressure in the expanded pipe when curing the same in its expanded,rounded condition.

With the trailing end of folded pipe 10 heated, as by using end heater152 previously described, to make it pliable, the conical portion oftorpedo plug 176 is driven into the trailing end of pipe 10, as shown inFIG. 19, until end cad 184 abuts the end edge of the new pipe, thusexpanding the end of the new pipe to a rounded shape conforming to-theouter diameter of cylindrical plug portion 182. An adjustable chainclamp 190 is used to clamp the expanded end portion of the new pipe tothe cylindrical portion 182 of the torpedo plug to seal the pipe to theplug.

Details of the chain clamp 190 are shown in FIGS. 20 and 21. The chainclamp includes a clamping plate 192 having a curved pipe-engagingsurface 193. The plate's convexly curved outer surface mounts a clevice194 between which a nut member 195 is pivoted. Nut member 195 receives athreaded rod 196 having a wrenching end 197. A clamping chain 198 isconnected to the opposite end of the rod. The chain is preferably atransmission chain or bicycle chain or the like. The chain is adaptedfor adjustable connection to an anchor post 199 on the outer surface ofclamping plate 192.

With the end of pipe 10 heated and pliable, and torpedo 176 inserted insuch end, clamping plate 192 is placed on the rounded pipe end, andchain 198 is wrapped around the cylindrical pipe end, cinched up astight as possible by hand, and then anchored to anchor post 199.Clamping pressure is then applied by rotating threaded rod 196 in adirection to shorten the effective length of clamping chain 198 using awrenching tool applied to wrenching end 197 of the rod. It is importantthat the clamp be easily tightened because the plastic pipe tends todeform when heated, and the clamp must be tightened in place during theprocess of heating and rounding of the new pipe.

With the torpedo plug clamped in place at the trailing end of the newlyinserted pipe, a steam hose connected to the plug connection 188. Hotsteam is forced through the length of the folded pipe, more specificallythrough the small passages through it, allowing the full length of thepipe to be heated. At the same time, the restriction imposed by the endclamp at the leading end of the folded pipe enables the pipe to bepressurized internally up to about 25 PSI. As the pipe becomes heatedand pressurized, it expands and rounds to its cylindrical shapethroughout its length, except at its clamped end portion.

When the new pipe is expanded and rounded to its desired dimension,usually against the inner wall of the existing lateral, the plastic pipeis allowed to cool while maintaining internal pressure through, forexample, the introduction of air under pressure, thereby enabling thenew pipe to cure in its newly rounded form. When the new pipe is cured,the chain clamp is released from its trailing end and the torpedo plugis removed.

Removing the Clamped End of the New Pipe

The next step is to remove the end clamp and still folded and clampedleading end portion of the new pipe from the remaining rounded portionof such pipe. This is accomplished by cutting the clamped and foldedleading end from the expanded and rounded new pipe as shown withreference to FIGS. 22 and 23.

In FIGS. 22 and 23 a severing means is shown for cutting off the foldedand clamped leading end of the expanded and rounded pipe 10 in theexisting pipe. The severing means comprises a power operated cuttingtool 200. The cutting tool includes a small high speed electric or airmotor 202 housed within a cylindrical motor housing 204 of substantiallysmaller diameter than the inside diameter of the rounded plastic pipe10. A flexible air hose or electric power cord 206 supplies power to themotor 202 from a remote source at the entrance opening to the existingservice lateral. A motor drive shaft 208 mounts a rotor 210 to which apair of cutting or flailing blades 212, 213 are pivotally attached atpivot connections 214 adjacent the outer ends of the rotor.

Motor housing 204 is encased in an inflatable rubber sleeve 216 which,when expanded, centers and anchors the cutting unit in place within therounded plastic pipe. A flexible air supply hose 218 supplies air underpressure for inflating sleeve 216.

Although the flail blades 212, 213 shown are steel, they could also bemade of chain or cable. They are designed to extend outwardly undercentrifigal force as rotor 210 rotates, to flail and cut plastic pipe10.

In use, cutting unit 200 is pushed down through the new plastic pipe 10after the pipe has been installed and rounded. The pushing can beaccomplished with a flexible fiberglass rod and with rubber sleeve 216deflated. The cutter is pushed into the existing lateral until itreaches the collapsed and clamped leading end. At this point, sleeve 216is inflated to anchor and center the cutting unit within the roundedplastic pipe. With the sleeve inflated, motor 202 is energized bysupplying it with power through air hose or electric cord 206. The motorrotates rotor 210 to activate flail blades 212, 213 until the blades cutoff the clamped and folded end of the plastic pipe. The severed endfalls into the main and can be retrieved later by conventional methods.

After the leading end of the pipe is cut off, sleeve 216 is deflated andthe cutting unit is recovered from the rounded plastic pipe simply bypulling on the air hose 218 and power cord 206 from the entrance end ofthe new pipe. The new lateral is now installed in the existing lateral,and after it is connected up with the portion of the lateral leadinginto building 96 (FIG. 7) it is ready for service.

Alternative Methods and Apparatus for Installing and Expanding the NewPipe in an Existing Lateral

FIG. 33 illustrates an alternative method of pulling the folded plasticpipe 10 through an access opening 98a into an existing lateral 90aintersecting a main pipeline 94a at an intersection 92a. At somedistance from intersection 92a the main 94a has a manhole 216 for accessinto the main. A cable winch 218 is stationed at manhole 216. Theleading end of a pull cable 220 is introduced into the existing lateral90a at access opening 98a and pushed down the lateral to intersection92a by a flexible fiberglass rod the leading end of which is equippedwith a gripper for gripping the leading end of the pull cable.

The leading end of the push rod is also curved so that when it reachesthe intersection, it can be directed around the sharp corner into themain. At this point the push rod continues to push the pull cable 220through the main, as shown at 220a, until the leading end of the pullcable reaches manhole 216. The leading end of the pull cable is attachedto the winch cable at 219. The trailing end of the pull cable 220, stillat access opening 98a to lateral 90a, is connected to the leading end offolded pipe 10 using one of the cable release methods previouslydescribed. The new pipe, after being heated in, for example, hot box 18to be made pliable, is pulled into existing lateral 90a by winchingcable 220 using winch 218 at manhole 216. The pulling continues untilthe leading end of new pipe 10 reaches intersection 92a. Then pull cable220 is released from the leading end of the new pipe using one of thepreviously described techniques. The new pipe is now ready for expansionand rounding within the existing lateral 90a using either the previouslydescribed method of rounding or another method to be described.

Inflatable Plug Method of Rounding Pipe

Another method and apparatus for expanding the newly installed plasticpipe within an existing service lateral are shown in FIGS. 25-29. Thismethod is known as the inflatable plug method. The inflatable plug 222used in this method is shown in FIGS. 25 and 26. It is used instead ofthe end clamp 144 (FIGS. 12-13) or end clamp 250 (FIGS. 39-41) to sealoff or restrict the inaccessible leading end of the new plastic pipe sothat such pipe can be pressurized, rounded and expanded. The plug isdesigned to be capable of holding at least 25 PSI of air pressure,expand to an outer diameter the size of the inside diameter of therounded new pipe, but not burst if unrestrained by the new pipe. Theplug should also be designed to withstand a temperature in excess of200° F.

The inflatable plug could be constructed of a single layer of flexiblematerial if a suitable material could be found to meet the foregoingspecifications. However, no such suitable material has yet been found.Therefore a two-layer construction of the plug is presently used. Theplug is composed of an outer canvas or other fabric tube 224 folded,shut and stitched closed at its leading end 225. The outer tube 224 hasan expanded diameter corresponding to the desired inside diameter of thenew pipe when rounded. The trailing end 226 of the canvas tube remainsopen. An expandable rubber inner tube or bladder 228 is placed insidethe canvas tube. The total length of the plug can vary from about onefoot to 20 feet depending on the application. The trailing ends of theouter canvas tube and inner rubber tube are gathered about a pipe stem230 providing an air hose connection 232 for an air or steam supply hose234 for supplying fluid under pressure to the interior of the innertube. The trailing ends of the outer and inner tubes are gathered aboutpipe stem 230 and tightly banded by a band clamp 236 to prevent leakageof pressurized fluid from the inner tube.

The inflatable plug as described is typically used in installing androunding new service laterals so that the previously described endclamps and end cutters need not be used. A typical method of using theinflatable plug is as follows:

The required length of folded plastic pipe for a given existing servicelateral is heated and rounded in the shop using, for example, the steamtube previously described. The hose 234 for pressurizing the plug isinserted through the length of the rounded plastic pipe with theinflatable plug attached, until the plug is positioned at the leadingend portion of the rounded plastic pipe.

At this point, the precut length of rounded plastic pipe is reheated,and refolded with the deflated plug and connected air hose folded insidefor field use. FIG. 27 shows the insertion of the air hose and connecteddeflated plug 222 into the rounded plastic pipe 10. FIG. 28 illustratesthe refolding of the pipe 10 with the deflated plug 222 and hose 234inside the folded pipe.

At the job site, the plastic pipe is heated and inserted while foldedand flexible into the lateral to be rebuilt. When completely inserted,the folded plastic pipe is heated with the plug still deflated bypassing steam through the pipe. When the full length of the installedplastic pipe has been heated, the plug is inflated via air hose 234 toexpand the plug and thus the still hot, pliable leading end portion ofthe plastic pipe 10 surrounding the plug to completely plug the leadingend portion of the plastic pipe. After the plug is inflated, the plasticpipe upstream of the plug Is pressurized by, for example, compressedair, rounded and expanded, with the air being supplied by a hose 236leading into the torpedo plug 176 at the trailing end of the new pipe asthe access opening 98.

After the new plastic pipe has been completely rounded and expanded to adesired diameter within existing lateral 90, and then allowed to cool,plug 222 is deflated and pulled out of the newly rounded pipe 10 by itsair hose 234. The newly installed plastic lateral is now ready forservice.

Other Methods of Using the Inflatable Plug

FIGS. 30-32 illustrate some other methods of using the inflatable plugjust described.

A slight variation on the method illustrated in FIGS. 27-29 is the useof the inflatable plug as a sliding plug during the pipe roundingprocess. According to this variation, referring to FIG. 30, inflatableplug 222 and its air hose is installed in prerounded plastic pipe 10 andfolded with the pipe as before, but with the plug positioned about sixinches or so from leading end 238 of the pipe, allowing such leading endto be folded as compactly as possible for ease of insertion into theexisting lateral. The folded pipe 10, with deflated plug 222 inside, isinstalled folded as before into the existing lateral. The trailing endof the new pipe is plugged by a torpedo plug 176, with air hose 234extending through a seal in the torpedo plug.

With inflatable plug 222 deflated, the folded pipe is steam heatedinternally throughout its length to render it pliable. Air hose 234,where it extends from the torpedo plug 176, is pulled tight and a clamp240 is placed on the hose 12 inches or so behind the rear end of thetorpedo plug. When the folded new pipe is hot, the inflatable plug isinflated. In addition the folded new pipe between the inflated plug 222and the torpedo plug 176 is pressurized with compressed air injectedthrough the torpedo plug via air line 236. The pressurization of the newpipe forces the inflated plug 222 to slide toward leading end 238 of thenew pipe until it is stopped by the abutment of clamp 240 against therear end of the torpedo plug. At this point the leading end, like therest of the newly installed pipe, will be completely rounded. Theinflated plug 222 is now deflated and pulled from the newly installedpipe.

FIG. 32 illustrates another method of using the inflatable plug 222 toplug, round and expand the new pipe within an existing lateral or otherconduit having access from only one end.

According to this method, the new pipe is inserted into the lateral in afolded condition using one of the previously described insertiontechniques and without the leading end clamp or inflatable plug to sealor restrict its leading or downstream end. However, at least about 10feet of extra length of the folded plastic pipe is left exposed at theaccess end to the existing lateral. The folded pipe is steam heatedinternally to render it pliable throughout its length. When hot, anexterior clamp 242 is applied to the folded pipe about 10 feetdownstream of torpedo plug 176. Then the upper ten feet or so of plasticpipe between the clamp and torpedo plug is rounded by injecting steamfrom line 236 through the torpedo plug into the upper ten feet of thefolded pipe. The rounded ten feet of pipe is then allowed to cool in itsrounded condition.

The torpedo plug 176 is now removed and inflatable plug 222 is insertedin at least a partially inflated condition for ease of insertion intothe rounded section of the new pipe. Torpedo plug 176 is reinserted intoone end of the rounded section of new pipe with air hose 224 from theinflatable plug extending through it. Now clamp 242 is removed from thenew pipe, and the inflatable plug 222 is deflated. The new pipe is steamheated internally again throughout its length to again render itpliable. When the new pipe is hot, inflatable plug 222 is partiallyinflated. The internal pressure within the new pipe, which may be steamor air pressure, is increased, and the partially inflated plug 222 ispropelled through the new pipe, which at this point is partiallyunfolded and partially rounded. When the inflatable plug 222 reaches thedownstream or leading end of the new pipe, it is fully inflated to plugthe end. The new pipe is now fluid pressurized, fully rounded, andcooled and thus cured in its rounded condition. When cured, inflatedplug 222 is deflated and pulled from the fully rounded pipe.

Remote End Pipe Seal

A method and means are also provided for sealing the space between thenew rounded pipe and the existing pipe wherever such pipes intersectanother opening, whether a manhole or another pipe. A typical pipeintersection would be at the downstream end of a building sewer linewhere it enters a sewer main.

The seal is simply a compressible rubber sleeve encircling theintersecting end of the folded new pipe. It is typically 1/4 to 1/8 inchthick but can be of any reasonable thickness. It is typically 12 to 24inches long but can be of any desired length.

When the leading end of the folded new pipe is installed and accessible,such as at a manhole, the sleeve can be slipped over the folded end ofthe new pipe before such end is rounded. Then, during rounding of thepipe end, the sleeve is rounded also. The new pipe is expanded duringthe rounding process until the rubber sleeve is compressed tightlybetween the new pipe and the existing pipe to form the fluid-tight seal.

For sealing the remote and inaccessible downstream ends of buildingsewer lines, a different method is used. An adhesive-backed rubbersleeve is used. The leading end of the folded new pipe is heated,unfolded and rounded before insertion into the existing pipe. Theadhesive-backed sleeve is applied to the rounded end, and the end isrefolded with the sleeve attached. Then the folded new pipe is insertedinto the existing pipe, using one of the previously described processes.

Use of the previously described expandable plug is the preferred methodof rounding and expanding the remote end to be sealed. With such plug,the expansion and hence the seal is more complete and more certain thanwith the other described methods.

Method of Removing Installed Thermoplastic Replacement Pipe from anExisting Underground Conduit

As previously noted, it is preferred that the thermoplastic pipe 10 bemanufactured in the folded shape shown in FIG. 8. Having been firstcooled and cured in such folded shape, the thermoplastic pipe retains amemory for such shape which tends to return it to such folded shapewhenever it is reheated and unrestrained. This memory for its foldedshape can be utilized to advantage when removing a damaged section ofsuch pipe from an existing underground conduit.

To remove the damaged thermoplastic pipe from inside an existingpipeline, the damaged pipe is heated by passing live steam through itand, if possible, around the outside of it. When hot, the damaged pipesection to be removed collapses to its original folded shape. Thiscollapse and refolding can be accelerated by connecting a vacuum pump tothe interior of the pipe to lower its internal pressure. When collapsedand folded, the hot plastic pipe can be pulled from the existingpipeline by a cable winch with the pull cable attached to an accessibleend of the collapsed pipe.

Heating and Forming Thermoplastic Pipe for Insertion

Heating the folded thermoplastic pipe for ease of insertion, especiallywhere bends in the existing pipe or conduit must be negotiated, or thenew pipe must be fed down through a small, deep vertical hole, isimportant. Several methods of heating for insertion have been describedincluding use of a hot box or a long steam tube. Another method is toheat the inside of the existing pipeline into which the thermoplasticpipe is to be inserted. According to this method, a short section ofpipe having a steam connection is connected to the trailing end of theexisting pipe to be repaired. A canvas closure on the trailing end ofthe steam pipe section is wrapped around the folded new pipe as it isfed through the steam pipe connection into the existing pipe to heat thenew pipe during its insertion. This method can also be used to advantagewith the other described heating methods.

The flattened, folded form of the rigid thermoplastic pipe shown inFIGS. 3 and 8 is also important because such form gives the pipe certainattributes unattainable with other pipes that may be collapsed orpartially collapsed solely for the purpose of reducing their overallcross sectional dimensions for insertion in an existing pipe. First, theflattened, folded form shown, when heated and pliable, can be storedconveniently and compactly in long or short lengths on a spool. Thespool in turn can be used for storage, reheating and feeding the pipeinto a conduit.

Second, the form of pipe shown, when heated and pliable, is capable ofbeing inserted into a pipeline around a sharp bend from a small verticalaccess opening, such as a manhole, and is capable of being installedaround sharp bends in the existing pipeline itself. For example, a rigidPVC pipe of a typical wall thickness-to-diameter ratio within the rangepreviously mentioned, when flattened and folded to the unique form shownin FIGS. 3 or 8, and heated to a pliable state, will have a ratio ofminimum bending radius-to-rounded outside diameter of between one andtwo. That is, a typical 4-inch diameter rigid PVC pipe, when pliable,flattened and folded as shown in FIGS. 3 or 8, can negotiate a curvehaving a radius of between 4 and 8 inches, depending on wall thickness,without damaging the pipe walls. Such a minimum bending radius isunattainable with other known forms of rigid thermoplastic pipe when intheir pliable states.

Third, despite the foregoing attributes when heated and pliable, thefolded pipe forms of FIGS. 3 and 8 can be reformed readily to a roundshape and cured to render it structurally rigid and sufficiently strongto withstand external earth and hydraulic pressures. Thus the installedthermoplastic pipe of this invention is truly a replacement pipe, notmerely a liner for a damaged existing pipe.

Having described the principles of my invention by what are presentlyseveral preferred embodiments and variations thereof, it should beapparent to persons skilled in this art that the invention can bemodified in various ways without departing from such principles. I claimas my invention the preferred embodiments and all modifications,variations and equivalents coming within the true spirit and scope ofthe following claims.

I claim:
 1. A method of manufacturing a thermoplastic liner forinstallation into an existing conduit in a desired non-circularcollapsed and folded form, comprising:extruding thermoplastic materialthrough a die to form a substantially tubular shape of a desired size;shaping the extruded tubular material exiting the die at a temperatureabove the temperature which the material is pliable to the desirednon-circular collapsed and folded form; and cooling the extrudedmaterial in the non-circular collapsed and folded form after shaping sothat the liner has a memory for the desired non-circular collapsed andfolded form such that when reheated to render it pliable, it retains thedesired non-circular collapsed and folded form.
 2. The method ofmanufacturing a thermoplastic liner of claim 1, including the step ofreheating the cooled thermoplastic material in non-circular collapsedand folded form to render it longitudinally pliable so that it can beplaced in a form suitable for storage.
 3. The method of manufacturing athermoplastic liner of claim 2, including winding the thermoplasticmaterial in non-circular collapsed and folded form onto a storage spoolas it is withdrawn from the reheating step.
 4. The method ofmanufacturing a thermoplastic liner of claim 2, wherein the liner isreheated by passing through a heating chamber.
 5. The method ofmanufacturing a thermoplastic pipe of claim 4, including feeding hotsteam into the reheating chamber.
 6. The method of manufacturing athermoplastic liner of claim 1, wherein shaping includes feeding theextruded thermoplastic material through calibrator means havingnon-circular openings for sizing and shaping the extruded thermoplasticmaterial to the desired non-circular collapsed and folded form.
 7. Themethod of manufacturing a thermoplastic pipe of claim 6, includingsubjecting the thermoplastic material to an external partial vacuum whenit is fed through the calibrator means.
 8. The method of manufacturing athermoplastic liner of claim 6, including removing the shaped liner inthe desired non-circular collapsed and folded form from the calibratormeans by tension.
 9. The method of manufacturing a thermoplastic linerof claim 1, wherein shaping into the non-circular collapsed and foldedform includes forming longitudinal interior passages along the liner andthe method further includes injecting a compressed fluid into theinterior of the thermoplastic material during shaping.
 10. The method ofmanufacturing a thermoplastic liner of claim 1, wherein shaping thethermoplastic material includes flattening the tubular material andfolding it longitudinally.
 11. The method of manufacturing athermoplastic liner of claim 1, wherein shaping the thermoplasticmaterial includes flattening the tubular material and folding itlongitudinally to form a short leg and a long leg and a rounded foldportion.
 12. The method of manufacturing a thermoplastic liner of claim11, including reheating the cooled thermoplastic material in flattenedand folded form to render it longitudinally pliable to be placed in aform suitable for storage.
 13. The method of manufacturing athermoplastic liner of claim 12, including winding the thermoplasticmaterial in flattened and folded form onto a storage spool.
 14. Themethod of manufacturing a thermoplastic liner of claim 1, wherein thethermoplastic material is polyvinyl chloride.
 15. A method ofmanufacturing a thermoplastic liner in a collapsed and folded form forinstallation into an existing conduit comprising:extruding thethermoplastic liner material through a die to form a tubular shape ofdesired size; shaping the resulting hot tubular shape exiting the die tothe desired collapsed and folded form; cooling the liner material in thecollapsed and folded form so that the liner has a memory for thecollapsed and folded form such that when reheated to render it pliable,it retains the collapsed and folded form; reheating the cooled collapsedand folded tubular liner to render it pliable; winding the liner in thecollapsed and folded form for storage.
 16. The method of manufacturing athermoplastic liner of claim 15, wherein shaping the hot tubularmaterial includes flattening the tubular liner and folding itlongitudinally to form a short leg and a long leg and a round foldportion.
 17. A method of manufacturing a thermoplastic liner in acollapsed and folded form for installation into an existing conduitcomprising:extruding the thermoplastic liner material through a die toform a tubular shape of desired size; flattening the tubular materialexiting the die and folding the liner to a flattened and folded form sothat it has a short leg and a long leg and a rounded fold portion;cooling the thermoplastic liner material in the flattened and foldedform after shaping so that the liner has a memory for the flattened andfolded form such that when reheated to render it pliable, it retains thedesired flattened and folded form; and storing the thermoplastic linerin the flattened and folded form by winding the liner on itself in alayered condition.
 18. The method of manufacturing a thermoplastic linerof claim 17, wherein the thermoplastic material is polyvinyl chloride.